Book Cipher

The book cipher can take a long time to crack, but it is really simple. To encode your message, take a book, or a long piece of writing, that you know the receiver of the message has, and find the words you need for your message. A small example of a message in this text would be 31 45 18 13 15 16 10.If you did it right, you would have ended up with "Your message is really simple to crack."